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Scientists Discover a New Cause of Melting Antarctic Ice Shelves

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Research Vessel Nathaniel B Palmer on the Thwaites Ice Shelf in Antarctica. Credit: Aleksandra Mazur

Researchers have discovered a process that contributes to the melting of Antarctic ice shelves.

An international team of researchers found that adjacent ice shelves play a role in destabilizing other ice shelves downstream.

of University of East Anglia In the UK, he led a study that identified that the amount of glacial meltwater flowing under the Thwaites Ice Shelf may be influenced by a small ocean circulation next to it. Warm water becomes accessible to the area under the ice shelf and the ice shelf melts.

The Thwaites Ice Shelf, one of the largest ice shelves in West Antarctica, has retreated rapidly over the past two decades and is the largest contributor to global sea level rise among Antarctic glaciers. supports the east side of

Thwaites Ice Shelf

Thwaites Ice Shelf, Antarctica. Credit: Karen Alley

Using a unique dataset collected by sensors placed under the Thwaites Ice Shelf, the researchers found that between January 2020 and March 2021, the shallow layer of the ocean beneath I observed it warmed up.

Much of this warming is due to the massive outflow of glacial meltwater from the Pine Island Ice Shelf further east into the area beneath the Thwaites Ice Shelf.

Thwaites Ice Shelf Borehole Drilling

Researchers will drill a borehole in the Thwaites Ice Shelf to install monitoring sensors underneath. Credit: Karen Alley

When the ocean melts the bottom of the ice shelf, glacier meltwater can mix with salt water to form a layer of buoyant water that is warmer than the surrounding water. This light, relatively fresh, warm water provides heat that melts the bottom of the Thwaites Ice Shelf.

Lead author Dr Tiago Dott of the UEA Center for Ocean and Atmospheric Sciences said: Circumpolar deep water, the warm waters of Antarctica, play an important role in melting the bottom of ice shelves. However, this study shows that large amounts of heat in shallow layers beneath one ice shelf can be provided by water originating from other nearby melting ice shelves. Therefore, what happens to one ice shelf can affect neighboring ice shelves. This process is important for areas with intense ice shelf melting, such as the Amundsen Sea. Because one ice shelf sits next to another, heat release from one ice shelf reaches the next ice shelf through ocean circulation. “

Dr. Dott added: Potentially existing circulation in other regions around Antarctica could predispose more ice shelves to intense basal melt, associated with prolonged warm conditions, resulting in global warming. It may further contribute to sea level rise. “

Researchers building a watchtower with atmospheric sensors

A researcher builds a watchtower with atmospheric sensors on the Thwaites Ice Shelf. Credit: Karen Alley

In January 2020, US colleagues drilled into the ice and installed sensors to monitor temperature, salinity and currents beneath the Thwaites Ice Shelf.

For more than a year, these sensors have been used to transmit data via satellite and identify changes in the ocean, such as changes in temperature and meltwater content. These observations led the researchers to conclude that excessive heat could not have occurred locally on the Thwaites Ice Shelf, as no strong melting was seen where the sensors were placed.

By combining this information with computer simulations to identify the origin of this heat, we find that water exiting the Pine Island Ice Shelf can access the area beneath the Thwaites Ice Shelf.

Mechanisms explaining how these areas access the Thwaites Ice Shelf were identified using model simulations and data collected by seal-mounted tags. Both indicated that circulation near the Thwaites Ice Shelf weakened in winter, allowing more heat to reach the shallow regions beneath the ice shelf.

Satellite imagery also showed that the 2020/2021 Southern Hemisphere summer was an anomaly due to the concentration of sea ice in areas near the Thwaites Ice Shelf.

Based on simulations and previous studies, the researchers hypothesize that circulation was weaker, so excess meltwater from adjacent ice shelves could not be displaced from the area by currents and entered the Thwaites Ice Shelf instead. I was.

This further reduced the intensity of this circulation, allowing the influx of water with a higher concentration of glacial meltwater beneath the ice shelf.

Ref: “Ocean variability under the Eastern Thwaites Ice Shelf Driven by Pine Island Bay Gyre Strength” Tiago S. Dotto, Karen J. Heywood, Rob A. Hall, Ted A. Scambos, Yixi Zheng, Yoshihiro Nakayama, Shuntaro Hygo, Tasha Snow, Anna K. Wåhlin, Christian Wild, Martin Truffer, Atsuhiro Muto, Karen E. Alley, Lars Boehme, Guilherme A. Bortolotto, Scott W. Tyler, Erin Pettit, December 21, 2022 , DOI: 10.1038/s41467-022-35499-5

データを収集した自動気象学-氷-地球物理学-海洋システム (AMIGOS) への資金提供は、米国の国立科学財団から受けました。 この研究は、英国自然環境研究評議会 (NERC) の支援も受けました。

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